1. Field of the Invention
The present invention relates to an electronic component manufacturing method, and more specifically, to a manufacturing method for an electronic component in which a cover layer formed of resin or the like is provided on a substrate.
2. Description of the Related Art
An electronic component in which a cover layer is provided on a substrate has been proposed. For example, such an electronic component is produced through steps illustrated in cross-sectional views of FIGS. 14A-14E.
That is, semiconductor chips 139 are mounted on a substrate 130, and resin 152 in a liquid form is dropped from a dispenser 151 and is then cured to cover the semiconductor chips 139. Since the height of a surface of the resin 152 sometimes differs between the center and the periphery or is not equal to a predetermined height, the surface of the resin 152 is ground with a dicing blade 154 so that the height of the surface of the resin 152 becomes uniform, and division into individual electronic components is performed by the dicing blade 154.
When a cover layer is formed on a substrate, the substrate sometimes warps. For example, as illustrated in a cross-sectional view of FIG. 13A, when resin is dropped into an area surrounded by a frame-shaped member 15 placed on the outer periphery of an upper surface 12a of a substrate 12 and is then cured to form a cover layer 16, as illustrated in a cross-sectional view of FIG. 13B, internal stress in a direction of arrow 16k remains in the cover layer 16, and this sometimes warps the substrate 12.
If the surface of the cover layer is ground with a dicing blade in a state in which the substrate remains warped, the height (thickness) of the cover layer with respect to the substrate varies in the substrate direction after grinding, and divided electronic components become uneven in height. If the grinding depth is decreased to ensure a predetermined thickness of the cover layer in all divided electronic components, the divided electronic components include a defective component having an excessive thickness of resin, and this sometimes decreases yield. In contrast, if the grinding depth is increased so that the divided electronic components have thicknesses within a predetermined thickness, failure occurs, for example, mounted components in the resin are exposed or ground.
To handle a resin layer in an electronic component with a suction nozzle, a ground surface of the cover layer needs to be flat. If the cover layer is ground, for that purpose, at a pitch less than the thickness of the dicing blade so that an unground portion does not remain, the dicing blade is prone to uneven wear, and the life of the dicing blade is shortened.
That is, as shown by arrows 7a, 7b, . . . , 7y, and 7z in a plan view of FIG. 10A, a cover layer 16 formed on a substrate 12 is sequentially ground at a predetermined pitch while moving a rotary blade 6 relative to the cover layer 16.
At this time, since end portions 6a and 6b of an outer peripheral surface of a typical dicing blade 6 are chamfered to prevent chipping, as illustrated in an enlarged side view of FIG. 12, if grinding is performed at a pitch equal to the thickness of the dicing blade 6, unground portions 16y remain.
If grinding is performed at a pitch less than the thickness of the rotary blade 6, only one side (right side in the figure) of the outer peripheral surface of the rotary blade 6 performs grinding, and the rotary blade 6 is prone to uneven wear, as illustrated in FIGS. 10B and 10C serving as enlarged side views along line A-A in FIG. 10A.
If grinding is continued with the unevenly worn rotary blade 6, unground portions 16z are formed on the ground surface, as illustrated in an enlarged cross-sectional view of FIG. 1, and therefore, it is necessary to replace the dicing blade. This shortens the life of the dicing blade.